The present invention relates to a wear-resistant aluminum alloy excellent in caulking properties and an extruded product using the same.
More particularly, the present invention relates to an aluminum alloy suitably used for automotive brake parts for which wear resistance to sliding parts and viscosity during plastic deformation such as caulking are required, and to an extruded product obtained by extruding the aluminum alloy.
As an alloy generally used to secure wear resistance, an alloy in which hard Si particles are distributed in aluminum by adding a large amount of Si, such as a 4032 alloy specified in Japanese Industrial Standards (JIS) H4140, has been proposed. Japanese Patent Application Laid-open No. 9-176769 discloses an alloy in which extrudability and machinability are improved while maintaining wear resistance by adding Si, Mg, and Mn.
However, in the technical field of automotive brake parts and the like, in which wear resistance in lubricating oil such as brake fluid is necessary, compressive strength is required in addition to wear resistance. Moreover, viscosity of the material is necessary during caulking for assembling the parts.
A technology of depositing Si dispersion particles in the aluminum alloy by adding a large amount of Si, as described above, in order to improve wear resistance is known in the art.
However, viscosity of the metal material is decreased by dispersing Si particles in the alloy due to its notch effect.
Moreover, extrusion formability is decreased.
Therefore, not only extrusion productivity, but also viscosity is decreased in the aluminum alloy obtained by merely increasing the amount of Si added. Therefore, it is difficult to apply such an aluminum alloy to parts obtained by machining an extruded product of such an aluminum alloy and assembled with sliding parts such as a piston or valve, since such parts are relatively subjected to sliding wear and required to have compressive performance against lubricating oil sealed therein.